If you need to make more than just a cup or two of tea, you can brew it all at once (and keep it warm) by making it in a coffee pot.

DIY web site WikiHow details how to do it, noting that it's quite useful if you need a large volume of tea—like if you're sick. It isn't all that different from making coffee, except you don't use a filter and you place a tea bag or two in the filter basket. Hit the link to see the step-by-step instructions.